<HTML><HEAD><TITLE>asin(+Number, -Result)</TITLE>
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<H1>asin(+Number, -Result)</H1>
Evaluates the trigonometric function asin(Number) and unifies the resulting
value with Result.


<DL>
<DT><EM>Number</EM></DT>
<DD>A number.
</DD>
<DT><EM>Result</EM></DT>
<DD>A variable or float.
</DD>
</DL>
<H2>Description</H2>
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to asin(Number, Result) is
   equivalent to
<PRE>
    Result is asin(Number)
</PRE>
    which should be preferred for portability.
<P>
   In coroutining mode, if Number is uninstantiated, the call to asin/2 is
   delayed until this variable is instantiated.

<P>

<H3>Modes and Determinism</H3><UL>
<LI>asin(+, -) is det
</UL>
<H3>Exceptions</H3>
<DL>
<DT><EM>(4) instantiation fault </EM>
<DD>Number is not instantiated (non-coroutining mode only).
<DT><EM>(24) number expected </EM>
<DD>Number is not of a numeric type.
<DT><EM>(20) arithmetic exception </EM>
<DD>Illegal arithmetic operation: Number is greater than 1 or less than -1.
<DT><EM>(141) unimplemented functionality </EM>
<DD>Argument is of type breal
</DL>
<H2>Examples</H2>
<PRE>
Success:
      asin(1.0, Result).           (gives Result = 1.5708)
      asin(-0,5, Result).          (gives Result = -0.523599)
Fail:
      asin(1, 0.0).
      asin(1, 3).
      asin(1, r).
Error:
      asin(A, 6.0).                  (Error 4).
      asin(2, Result).               (Error 20).
      asin(4 + 2, -0.279415).        (Error 24).



</PRE>
<H2>See Also</H2>
<A HREF="../../kernel/arithmetic/is-2.html">is / 2</A>
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